The present invention relates to a stereoscopic projector, and more particularly to a method and an apparatus for driving projecting lenses in a stereoscopic projector wherein a pair of projecting lenses are integrally driven, so as to match (coincide) two images on a screen and simultaneously focus the images on the screen for producing a stereoscopic image, thereby avoiding a keystoning phenomenon.
Conventional stereoscopic image projectors, as shown in FIG. 1, generally comprises image-projecting units 1a and 1b each of which includes lamps 4a and 4b, spherical reflecting mirrors 3a and 3b, focusing lens devices 5a and 5b, slide films or LCD (Liquid Crystal Display Panel) panels 6a and 6b, and projecting lenses 7a and 7b. The units 1a and 1b are individually driven, in order to match two images and thus produce a stereoscopic image on a screen S. Specifically, producing the stereoscopic image on the screen S is accomplished by focusing an image from one unit 1a on the screen S to produce a distinct image, and then moving vertically and laterally another image focused on the screen S from the other unit 1b. Therefore, it is necessary to move vertically and laterally the unit 1b by itself.
In such a conventional stereoscopic projector, however, optical axes La and Lb are inclined at a certain angle with respect to the central axis L of screen S, so that left and right images on the screen S are projected in the shape of a trapezoid as shown in FIG. 7A. Thereby, a keystoning phenomenon is generated, that two images are not completely matched or coincided together, and thereby distorted.
Consequently, such a conventional projector has a disadvantage of increasing the fatigue of viewer's eyes in viewing stereoscopic images, due to the generated keystoning phenomenon. In addition, there is a disadvantage that matching images on the screen S becomes troublesome and inconvenient, because two image-projecting units 1a and 1b are individually driven and adjusted.